Mackie 1604 VLZ noise problem

[Marco Pancaldi]

I need here some help from the experts:

in my Mackie mixer, after about one hour of clean monitoring, the headphones out starts to make a (light but annoying) random-crackling noise, much like a defective transistor ot tube.

1 - The noise remains even when I switch off all the assign buttons (mains, subs, tape), so I think it't not due to channels, returns or noisy sources.
2 - The noise goes away when I set the control room-headphone volume to minimum, so the problem is before the pot.

Now, in this circuit section there is only one opamp (njm4560), but I'm confused from some active components (opamps and FETs) from the SOLO section. In other words I'm asking myself if a problem in the SOLO section can inject the crackling, static-like noise in the control room bus.

I can't insert here the original schematic, but you can find it at
http://www.gyraf.dk/schematics/schematics.html
the CR section is at page 8.

Any advice welcome
many thanks

 

[SonsOfThunder]

Try to reflow all the solder joints on and around the NJM4560. If that doesn't fix it, probably replace the 4560.

HTH!
Charlie